Conventionally, various polymers are used in fields of plastic and so on by utilizing their functions. However, in the present condition, only a few of them have a degradation under natural environment (biodegradability).
It is known that, among those polymers, polyacetals with a substituent, such as carboxylic ester group, directly linking to their main chains, have excellent biodegradability (JP-A-54-052196 and EP 0384911A2). However, a polyacetal with the carboxylic ester group has problems in that it is unstable to acids or alkalis and therefore easily hydrolyzes.
In addition, a polyacetal with a carboxylic salt group directly linking to its main chain is recently used as a detergent builder, but it is desired to further enhance the detergency of this polyacetal.